Female breast cancer has surpassed lung cancer as the most commonly diagnosed cancer, while lung cancer remains the most deadly, the American Cancer Society announced Thursday.
Thursday is the annual World Cancer Day. A new study found that last year, 10 million people worldwide died of cancer, and medical professionals diagnosed an estimated 19.3 million new cancer cases.
The report, authored by scientists from the American Cancer Society and the International Agency for Research on Cancer, said 2.3 million cases of female breast cancer were diagnosed in 2020, accounting for an estimated 11.7% of all new cancer diagnoses last year. Lung cancer ranked second, with 11.4% of new diagnoses. Colorectal cancer accounted for 10%, prostate cancer 7.3%, and stomach cancer 5.6%, the report said.
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Lung cancer remained the leading cause of cancer deaths. Lung cancer killed 1.8 million people worldwide, which made up 18% of all cancer deaths in 2020, the report said.
While female breast cancer was the most commonly diagnosed type in 2020, the report said the disease accounted for only 6.9% of cancer deaths. Colorectal, liver and stomach cancer were all more deadly than breast cancer, the report said.
The findings also pointed out disparities between countries with higher levels of economic development and those that are still developing. The American Cancer Society said people die of lung cancer 3 to 4 times more often in lower-income countries, largely due to higher rates of smoking there.
Women in developing countries died of breast cancer at higher rates as well, the study found. Hyuna Sung, PhD, lead author of the report and principal scientist at the American Cancer Society, said the disparity was due to their cancer being caught in late stages.
"Efforts to promote early detection, followed by timely and appropriate treatment, are urgently needed through the implementation of evidence-based and resource-stratified guidelines," Sung said.
The American Cancer Society said the report does not reflect the impact of COVID-19, as the estimates were made from data collected prior to the pandemic, but the World Health Organization said Wednesday that the COVID-19 pandemic has exacerbated problems of late-stage diagnosis and lack of access to treatment, particularly in low- and middle-income countries.
Doctors and health officials in the U.S. have raised concerns about the potential impact of people delaying preventive screenings like mammograms and colonoscopies.
A World Health Organization report also found that the pandemic disrupted cancer treatment in more than 40% of countries surveyed.
"In addition to having to cope with the disruption of services, people living with cancer are also at higher risk of severe COVID-19 illness and death," the WHO said in a statement Wednesday, adding that cancer research and clinical trials had also been delayed during the pandemic.
Breast cancer rates have been increasing in countries where rates were previously low, the American Cancer Society study found. The report's authors said the trend could be linked to an increase in breast cancer risk factors, such as excess body weight, physical inactivity, alcohol consumption and women having fewer children or starting to have children later in life.
The report projects that in 2040, the world will see about 28.4 million new cancer cases, about 47% more than 2020. Cancer rates are increasing more rapidly in developing countries, the report noted.
The authors warn, "The increasing burden of cancers associated with social and economic transition may overwhelm health care systems in many lower income countries if left unchecked."